This assumes you've already setup the OpenSSH server on the machine.
First, you will need these packages installed in this order:
Now, you must define your exports before nfsd will start. You do this by altering /etc/dfs/dfstab. To share /export/install for instance, where I have the Solaris installer files, I would add this line:
share -F nfs -o ro /export/install
This line gives everyone read-only access to my install files.
Now, nfs can be started and made to start at boot with these commands:
svcadm enable -t nfs/server
svcadm enable nfs/server
You can check to see if everything is working with a showmount -e.